Effects of Weight and Drag

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Mad Rocketeer

Well-Known Member
Nov 30, 2009
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My son, Jonathan, wanted me to post this one.

He is fascinated by the fact that a rocket like the Quest Pipsqueak can fly higher on a C motor than a larger rocket like the Estes Eliminator can on an E motor. He understands the effect of weight and drag on the result. That boy's turning into a fine rocketeer! :D

He also wants me to mention his upcoming birthday. I'll soon have a "ten-ager". :eek: ;)
Have him try to think of it this way.

For a rocket to perform perfectly and get maximum altitude it needs the following.

It needs to be infinitely light during boost...not really possible but the lighter the better.

And to get the maximum altitude after the motor burns out, it needs to have infinite mass (mass x velocity=~~) Again not possible.

So a model need "optimum weight".

Let him think about THAT!

That'll make the neurons grow!:D

And an early Happy Birthday!
Jonathan liked that. His brain cells are growing already. :D

He wanted me to post a note about his Baby Bertha. The first time we took it out to fly, toward the end of the day, with the light dimming but not yet twilight, we flew Baby Bertha on its first C motor. It put on a nice show. There was a good view of the fire as it went up, and the ejection gave a neat fireball effect in the dimming light. No damage, and a safe recovery nearby. I credit the short tube and the lessened sunlight with giving us a nice view of the flare that every rocket probably creates but hides at ejection. First time I'd seen it though.
You'll be amazed at the amount of fire and flame we can't see during daytime operations. Dusk. before the sun sets behind the horizon is a great time to experience this. but remember as soon as the sun sets below the visible horizon all launches must stop. If you get a chance to attend a full waivered night launch the show is fantastic.

You might mention to Johathan, Optimal weight is that elusive balance between mass and thrust giving the best overall "throw weight". Girth (frontal area) also makes a great difference, as does the forward shape. it's all connected:D

Another major factor is Finish. Turbulence at the boundry layer microns above the models skin makes a huge difference in altitude performance. A rough unfinished model will get as much as 20% less altitiude as an identical model with a babies butt smooth seamless finish. Heres the test examples we ran.
Yep. I'm aware of the rules on night flying, and we were definitely legal. It was dim enough to get a nice effect at launch and ejection, but light enough to make recovery of the landed rocket a snap. As a night flight, it would have been all that much more awesome.

When I do a night flight, I'll want to do the bright LED thing. Maybe a dozen or so bright LEDs with resistors and a small battery, stuffed into a clear payload tube.

Nice picture. Shock & Awe. Downright beautiful too.
Jonathan wanted me to mention his Wacky Wiggler. He's fascinated with that recovery method. (To tell the truth, so am I. I'd like to make a scratch-built on a similar concept, perhaps with multiple streamers at the joints.) He's eager to build his WW kit. I'm eager to see it fly. I definitely think we'll be flying it on C motors though, as I understand it has stability problems on smaller stuff (especially A motors) and that it lands near the pad on virtually anything.

Hmmm. How about a HP altitude bird or mach-buster with a multi-section first stage recovery (perhaps with streamers too) and a couple of chutes as a second stage. It has potential. :D